This invention relates to a pneumatic plug device and more particularly to an inflatable fabric bag plug device. The fabric bag plugs of the present invention are used to seal low-pressure pipes or conduits that convey fresh water, natural gas, petroleum products, and other low-pressure fluids.
Although fabric bag plugs have been proposed and used in the past, several shortcomings have continually existed with the structures of these plugs. For example, prior art plugs made of fabric material have not been found to be sufficiently abrasion and puncture resistant to be suitable for extended use in a construction environment. Further, such bag plugs have been limited in usage range in that their diameters upon inflation have been restricted as to expansion. Due to the composition and structure of the prior art devices, it has also been difficult to maneuver and secure such fabric plugs in a pipeline. For example, tethering structures have been found inappropriate to use with prior art devices because their respective structural integrities may be compromised when the plugs are subjected to full usage pressures in a pipeline.
It has also been found difficult to manufacture prior art fabric bag plugs that are leak resistant on a consistent basis. It has been found, for example, that the fiber structure in the fabric material used to manufacture bag plugs may result in the development of slow leaks upon inflation of the bag plugs. The leak cause has been found to be the wicking action set up by the fiber configuration in the fabric material utilized. The fiber configuration itself, therefore, creates escape paths along the fibers of the fabric material to permit air from the interior of the plug to leak from the inflated plug body. Therefore, it has been found difficult and costly to consistently manufacture a prior art plug that prevents leakage at the fabric edges upon the inflation of the plug due to the air channels that form in the fabric weave. The bag plug structure of the present invention overcome the shortcomings of the prior art plugs.
The present invention differs from the prior art in its structure and in the materials used in its structure. The plug body of the present invention utilizes at least one plug body fabric portion, although multi-portion body configurations may be utilized in accordance with the teachings of the invention to provide leak resistant plugs. The utilization of rectilinear flexible portions and sealing strips in the bag plug of this invention provides a means to assembly a plug with less stringent tolerances than those required in the assembly of prior art devices.
An adhesive, and preferably a contact adhesive, is used to bond the fabric to form the plug body, and importantly, capping strips are bonded over both the interior and exterior seams of the plug body. The cap strips are bonded in a manner to cover all fabric edges to prevent the leakage caused by the air channels set up in the fabric weave upon plug inflation. The materials of construction of the present invention result in a leak resistant, inflatable fabric plug device that may be constructed in an efficient and consistent manner. The resultant plug structure overcomes the difficulty and shortcomings of the prior art devices.
The object of the present invention is to provide an inflatable fabric bag plug that is leak resistant and suitable for use in low-pressure pipelines. It is also an object of this invention to provide a light-weight, foldable, easy to handle, inexpensive to manufacture fabric bag plug which is usable in low pressure pipelines and which is accessible through small access ports.